Add nlohmann/json to include/ (pytorch#2829)

Summary:
- Add nlohmann/json to include/ now that c10d requires this (see pytorch/pytorch#129505)

Pull Request resolved: pytorch#2829

Reviewed By: jianyuh, spcyppt

Differential Revision: D59649047

Pulled By: q10

fbshipit-source-id: 9c57c55b59bfd64094b1d73e2b43294c32ec6fd6

Author: q10

.gitmodules

@@ -13,3 +13,6 @@
 [submodule "external/cutlass"]
 	path = external/cutlass
 	url = https://github.com/NVIDIA/cutlass.git
+[submodule "external/json"]
+	path = external/json
+	url = https://github.com/nlohmann/json.git

external/json

@@ -31,6 +31,7 @@ set(fbgemm_sources_include_directories
   ${THIRDPARTY}/cpuinfo/include
   ${THIRDPARTY}/cutlass/include
   ${THIRDPARTY}/cutlass/tools/util/include
+  ${THIRDPARTY}/json/include
   ${NCCL_INCLUDE_DIRS})
 
 
@@ -41,11 +42,6 @@ set(fbgemm_sources_include_directories
 file(GLOB_RECURSE asmjit_sources
   "${CMAKE_CURRENT_SOURCE_DIR}/../external/asmjit/src/asmjit/*/*.cpp")
 
-set(third_party_include_directories
-  ${THIRDPARTY}/asmjit/src
-  ${THIRDPARTY}/cpuinfo/include
-  ${THIRDPARTY}/cutlass/include)
-
 
 ################################################################################
 # Optimizer Group Definitions

fbgemm_gpu/FbgemmGpu.cmake

@@ -24,6 +24,7 @@ set(fbgemm_sources_include_directories
   ${THIRDPARTY}/cpuinfo/include
   ${THIRDPARTY}/cutlass/include
   ${THIRDPARTY}/cutlass/tools/util/include
+  ${THIRDPARTY}/json/include
   ${NCCL_INCLUDE_DIRS})
 
 set(experimental_example_cpp_source_files

fbgemm_gpu/experimental/example/CMakeLists.txt

@@ -22,6 +22,7 @@ set(fbgemm_sources_include_directories
   ${THIRDPARTY}/cpuinfo/include
   ${THIRDPARTY}/cutlass/include
   ${THIRDPARTY}/cutlass/tools/util/include
+  ${THIRDPARTY}/json/include
   ${NCCL_INCLUDE_DIRS})
 
 set(attention_ops_sources